This invention relates to a damper of piston-cylinder type used as a stock absorbing means.
It is well known that as various shock absorbing devices including a bumper mounted on a rolling stock, for example, an automobile use is made of a piston-cylinder type damper having an operational medium filled in a liquid-tight fashion into the interior of a cylinder.
With such a damper the pressure of an operational medium is changed due to the variation of an inner volume of a cylinder as caused by the reciprocating movement of a piston or due to a temperature variation. In an attempt to control such pressure change in a suitable way and improve or stabilize the shock absorbing function of the damper, an air chamber is provided within the cylinder. The air chamber is designed to be contacted directly with the operational medium or be contacted indirectly with the operational medium through a partition wall, such as a free piston, slidably disposed within the cylinder. In the former case, a direction in which a damper is mounted is restricted. For example, a damper designed to be used in an upright state can not be used in a horizontal direction. In the latter case, when the partition wall is slidably moved along the inner surface of the cylinder, no smooth movement is effected. Furthermore, it is very difficult to attain a complete seal between the outer peripheral surface of the partition wall and the inner surface wall of the cylinder and there is a fear that air will be introduced into the operational medium.